1. Field of the Invention
The invention concerns devices enabling the irradiation of both faces of a product by means of an accelerator of charged particles.
2. Description of the Prior Art
A known way to obtain better long-term preservation of food products is to subject them to ionizing radiation. To this effect, the food products are moved in front of a source of radiation, the particles of which strike said food products on one side. A treatment, such as this, of only one face of the products is not enough when these products are in the form of packets of varying thicknesses. A double-sided treatment may be achieved by two successive passages of the packets after they are turned over. This kind of turning over is not possible when the products are loose or in liquid form. Hence, in this case, two radiation sources are used, placed on either side of the device on which the products are flow past, so as to simultaneously irradiate both faces of the products.
For double-sided or dual-face irradiation, there is a description by the applicant, in the French patent application No. 23906392, of a device for the dual-face irradiation of a target with two opposite faces. This irradiation device comprises a charged particle accelerator, for example electrons, associated with a microwave frequency generator so as to give high frequency pulses of charged particles. The beam of charged particles is applied to a horn-shaped scanning chamber where it is subjected, at its entry, to a variable magnetic field, to obtain a deflection of the beam by an angle on either side of the axis of symmetry of the horn. An aperture is made in the wide part of the horn. On one side of the axis of symmetry, this aperture covers half of the aperture of the horn, and is provided with two windows transparent to the beam. The product to be irradiated is moved between these windows. Beyond this aperture, the beam is subjected to a continuous magnetic field which makes the beam turn back by 180.degree. when it scans the other half of the horn with respect to the aperture. By this arrangement, the beam irradiates one of the faces of the product when it scans that part of the horn which includes the aperture, and the other faces when it scans the other part following the return of the beam.
The device described in the above-mentioned patent has the following drawbacks. It occupies a great deal of space heightwise, for the accelerator producing the electrons and the scanning and magnetic deflection devices are superimposed heightwise.
A second drawback is that it does not enable any monitoring of the energy of the flux of the electrons given by the accelerator, and the result thereof is a lack of uniformity of the ionizing treatment.
A third drawback is that the flux of electrons striking the upper face of the product to be ionized is divergent and that, consequently, a major part of the available energy is not used.
A fourth drawback is that the ionizing intensity of the part of the product which is in the vicinity of the axis cannot be monitored.
An aim of the present invention, therefore, is the making of a device for the dual-face irradiation of a product which does not have the above-mentioned drawbacks.